The present invention is generally directed toward controlling the ascent and descent of lifting arms of a hydraulically operated lifting device. The invention is more particularly directed toward controlling lifting devices of the type used for refuse collection vehicles. The invention is yet more specifically directed toward briefly controlling the ascent and descent of the lifting arms for dynamic accurate weighing of.
The invention is particularly directed toward a two-way valve for use in bypassing the main operation lifting circuit and main operating valve in order to control the lifting arms wherein a sensor generates an analog signal received at an analog/digital converter and a microprocessor that calculates the weight.
My presently co-pending application Ser. Nos., 07/488,679, now U.S. Pat. No. 5,065,828; 07/614,871, now U.S. Pat. No. 5,038,876; 07/614,870, now U.S. Pat. No. 5,064,008; and, 07/614,869, now U.S. Pat. No. 5,065,829, disclose hydraulic control systems useful for refuse vehicles that provide for static and dynamic weighing utilizing a bypass circuit that bypasses the lift circuit of the main hydraulic system. The bypass circuit allows for a controlled motion through a defined path determined by proximity switch means. To make the weight calculations the lift arms are, however, have to move controllably downward from one reference position to another for both gross and new weighing. While the systems disclosed in my previous applications are effective, they are in part limited by requiring both the gross and tare weights to be calculated only when the lifting assembly descends through a certain range. The information in these applications is incorporated herein by reference.
The present invention improves upon my previous inventions in these noted pending applications by providing a unique two-way valve arrangement that is cooperative with the main operating valve and the lift circuit of the lifting arms of a hydraulic lifting apparatus, such as a refuse vehicle. The two-way valve has two separate bypass flow paths through whereby the gross weight may be calculated dynamically while lifted and the tare weight calculated dynamically while the container descends. A microprocessor captures the full and empty weights at the same range of arm travel, up and down, due to the operation of proximity sensing means.
The present invention may utilize a hydraulic transducer as a weight sensor located in a flow chamber of the two-way valve, or alternately a tensiometer may be mounted on the lift arms. These weight sensors send analog signals in proportion to the pressure or strain, respectively exerted thereon to a programmed microprocessor for calculating the gross and tear weights during the time that the lift arms are in a pre-determined location relative to a proximity switch. The use of a tensiometer, strain gauge or load cell avoids the calibration problems often caused by the fluctuating hydraulic fluid temperature levels in high pressure lines, when a hydraulic pressure transducer is used temperature probes are helpful to send a temperature signal to the microprocessor, which program will take the temperature level into account in the calculation.
Accordingly, it is a primary goal of the invention to provide for a control system for hydraulic lifting devices that operates in conjunction preferably with a tensiometer attached to the arms, and also with a hydraulic transducers fluidly communicating with the lift circuit of the hydraulic system, for dynamically weighing full and empty lifted containers, respectively.
An important goal of the invention is to make the weight calculation of the full load while it is lifted and the empty container as it is lowered.
It is a very important goal of the invention to provide for a bypass system which taps off from the lift circuit of the lift arms to direct fluid to a unique two-way valve for controlling the ascent and descent of the lift assembly, whereby accurate weighing takes place during the controlled phase.
It is an allied goal of the invention to provide a bypass circuit in cooperation with a two-way valve that is useful for operation with either a hydraulic transducer weight sensor cooperative directly with the valve, or a tensiometer/strain gauge weight sensor located on the lifting arms; sending analog weight/proportional signals in both cases based upon the activation of a proximity switch whereby weighing takes place at substantially the same position for every load in order to insure accuracy.